hello there.
i didn’t try the default Linux launcher yet but compiling (RHEL9) always worked quite well.
here are some links regarding library`s that you might need to use
apparently qt5-default was set up in an interesting way on Ubunto a while ago and so the combination package is not that available, but you should be able to build the parts yourself (in the end -default is just a combination off other packages)
here`s a link to the qt5 version (apt - qt5-default not in Ubuntu 21.04 - Ask Ubuntu) but the same applies for qt6
i assume that qtbase5-dev is now qt6-base-dev (this also includes “qt6-qmake” ← this dost really exist any more but it was separate in qt5)
https://ubuntu.pkgs.org/24.04/ubuntu-universe-amd64/qt6-base-dev_6.4.2+dfsg-21.1build5_amd64.deb.html
and then you have this:
https://ubuntu.pkgs.org/24.04/ubuntu-universe-amd64/qt6-tools-dev_6.4.2-3build3_amd64.deb.html
what replaces the qtbase5-dev-tools in qt6
hope that enough if not let us know.